Control circuits



March 12, 1940.

Filed March 27, 1937 Source T T L? E Pact/fie;- Plaze Circuzz /5 /7 /3 /7 9 L1. 4 a B 5 E T% 3/ 57%: 23 3/ 5 :1 A. 29 29 71 27775 Dans? fidfli i WITNESSES: INVENTOR m Henry MJa/zizsoiz.

Patented Mar. 12, 1940 UNITED STATES CONTROL CIRCUITS Henry V. Johnson, Springfield, Mass., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 27, 1987, Serial No. 133,417

5 Claims.

My invention relates to the field of radio, and more particularly to a control circuit for use in connection with radio transmitters.

It is often desirable, from an economic viewpoint, to operate a plurality of transmitters from a common source of supply, and sometimes necessary to do this, where only one source of supply is available.

In systems of this character, where the power source constitutes a low voltage alternating current supply which is stepped up, rectified and filtered, the transmitters are connected in multiple to the high voltage direct-current side of the common supply source, which often has to deliver plate voltages in the neighborhood of 15,000 volts and a load current up to 2 amperes per transmitter.

It is not always essential in the operation of the system, that all the transmitters be operating at the same time, and very often it is necessary to disconnect one or more of the transmitters, either because it is not desired to utilize them at the time, or because of some transient or overload condition occurring in the circuits of one of the transmitters.

In prior practice it was necessary in order to connect or disconnect one or more of the transmitters at will, or during the established interval of transient or overload conditions, to open the power supply circuit on the low voltage alternating current side. After the entire system has been thus detached from its source of voltage, the particular transmitter desired to be removed from the circuit, was then disconnected and the source of potential supply again applied in the usual manner. It will be apparent that this procedure necessitated suspension of service for an appreciable time, for those transmitters which were desired to be kept in operation and thus introduced interruptions in the scheduled transmission.

Attempts have been made to solve the problem of permitting the individual transmitters to be switched out of circuit on the high voltage direct current side, so that the operation of the remaining transmitters may not be disturbed, in the .event of an overload condition or in the event when it was desired to remove one of the transmitters from the air. Such attempts, however, have not been wholly satisfactory by reason of the difiiculty involved in designing suitable switching apparatus for operation at such high direct-current voltages and such heavy loads. Arcing across the opening contacts constituted a most troublesome factor.

It is an object of my invention to provide a system for enabling one to disconnect a transmitter on its high voltage direct-current supply source without noticeably eifecting the operation of other transmitters connected to the same supply source.

A further object of my invention is to enable the switching of a transmitter on the high voltage direct current end of its supply source without introducing arcing difiiculties across the switching contacts.

A further object of my invention resides in the provision of a control system which shall automatically disconnect a transmitter upon the establishment of an overload condition, without necessitating any noticeable interruption of the operation of other transmitters which derive their potential from the same supply source.

Additional objects of my invention will be brought out in the following description of the same when taken in connection with the accompanying drawing, wherein the single figure constitutes a schematic diagram of a potential supply source feeding a plurality of transmitters in multiple, and a control circuit for accomplishing the objects of my invention.

. The transmitting system constitutes a plurality of individual transmitters l, 2 and 3 respectively connected in multiple to the high voltage direct current end of a power supply circuit which in the example shown, constitutes a three-phase I alternating current, low voltage supply '5 which is stepped up, rectified and filtered to obtain the high voltage direct-current plate potential for the transmitters. Each of the circuits to the transmitter contains a pair of normally closed contacts 9 and an overload relay coil iii in series with the transmitter.

The pair of closed contacts 9 in the line to its respective transmitter is associated with a relay l l which is provided with four pairs of contacts 9, l 3, l5 and [7. Two pairs of these contacts 9 and IT including the pair in the circuit to the transmitter are normally closed during operation of the transmitters, whereas the remaining two pairs l3 and I5 normally remain open.

The overload relay I0 in each of the trans- IrL tter branch circuits is provided with two pairs of contacts 19 and 2|, one pair IQ of which is nor mally closed and the other pair 2| being normally open.

In addition to the relays identified above, the control systemutilizes an additional relay 23 having four pairs of contacts, three of which designated by reference numeral 25 are located in the 3 phase lines to the rectifier, and during the application of plate excitation to any of the transmitters, these three pairs of contacts are normally in closed position. The fourth pair of contacts ill of the relay are open when the other three pairs are closed and vice-versa.

The e r gement and interconnection of these relays contacts are such that the relay windthe main alternating current contacts cted from a source of excitation in the normally closed contacts. id of I relays iii and normally closed contacts ll of switch The co-ntactor windings in all connected in parallel circuits, each parallel =ch comprising the coil 5 l, a pair of normally closed associated contacts I! and the normally open contactassociated with the overload relay ill. The normally open contacts Ell of the main alternating current relay winding are common to all the branch circuits, and the circuit across the source of excita- Across each of the normally closed contacts Ell cl ch of the overload relays it is connected a 1 ally open contacts l3 associated with the coil sponding contactor winding 5 l and normally closed contacts of switch id.

each of the normally open contacts 2! of each of the overload it is connected a 3 of normally open contacts associated with i. spending switch ill. lT'he no really open contacts 55 associated with 01'' he c ntact windings l l are connected in series with their associated winding across the control source of potential through a manually controlled but normally closed circuit opening device cooperation and sequence of operation ..ong the various elements of the con- Upon the occurrence of such a g c; overload relay ill in series with is will become excited to the exopening its normally closed contacts 59 its normally open contacts 25 and tag itself in this condition. Opening of the rally closed contacts l9 interrupts the series through the normally closed contacts it of the other overload windings lli, normally closed contacts ll of the switches ill, and the winding of the main alternating current breaker.

rectifier The breaking of the circuit through the op oi these contacts is immediately followed the closing of the normally open cont icts associated with the same winding. This .pletes a circuit through the contacts-r windll through the normally open contacts of the overload relay which normally open concts have previously been closed due to the opicn or" the overload The excitation cirto the contactor winding ll also includes a till disconnect transmitter No. i from the source of supply on the high Voltage side, through the ope n of the normally closed contacts il in th the transmitter. The second pair to of normally closed contacts S? which have now been opened, break the excitation circuit to the winding H, which circuit included the contacts ill or the main breaker coil 23, but the excitation is not lost as the coil II has been connected directly across the control supply source through the closing of a pair of its normally open contacts [5. This acts as a locking circuit to maintain this relay winding in a state of continuous excitation to thereby maintain the troublesome transmitter disconnected from the circuit. The excitation of the relay winding H at this point has also become independent of the normally open contacts 2'! of the main breaker.

Since the normally closed contacts of the overload relay are now locked in open position, they serve to maintain the circuit through the main breaker winding 23 open and thereby prevent its excitation, it is essential to provide some means for permitting the main breaker winding to receive excitation to reclose the contacts 25 which connect the alternating current source to the rectifier. This comprises the purpose of the remaining normally open contacts l3 of the container relay H, which normally open contacts are connected in shunt to the normally closed contacts ill of the corresponding overload relay ill. The normally open contacts ill at this stage of operation of the control circuit are now in closed condition due to the permanent excitation of its associated relay winding H, and it, therefore serves to replace the normally closed contacts E9 or" the corresponding overload relay H] which contacts are now in open condition. Thus, the breaker winding again becomes energised recloses the circuit to the rectifier to provide and supply the high voltage on the directcurrent side to the remaining transmitters.

Should it be desired to disconnect a transmitter from the D. C. power source this may be accomplished by operating switch an, associated with this transmitter, such that its normally closed contacts ti open and its normally open contacts :32 close. The sequence of operation is exactly the same as when overload relay it operated except normally closed contacts 4| of the switch to are substituted for normally closed contacts it of overload relay ill and the normally open contacts 42 of switch 4d are substituted for normally open contacts 21 of overload relay Hi.

The sequence or operation of the components of the control circuit as just described occurs so quickly, that a transmitter may be disconnected from the circuit and the remaining transmitter replaced in operation within an exceedingly short period of time of the order of oneighth ci a second. Insofar as this effects the operation of the remaining transmitters, their operation from all practical purposes has been essentially uninterrupted and in fact the transmitters are efiectively maintained in operation during the switching process.

By reason of the fact that the system is first opened on its low voltage alternating current side, the disconnecting or any one of the individual transmitters on the high voltage direct current side during the brief period of interruption of the alternating current supply, occurs without any sign or tendency to are at the contacts where the opening of the circuit on the high voltage side occurs, namely at the contacts 9 located in the circuit to the transmitter.

As a precaution against the possibility of extreme overload conditions injuring the overload relays ill, a resistor 3! is connected in series therewith and another resistor 33 in parallel.

In order to replace a transmitter on the air, which has previously been removed due to an overload condition, it is only necessary to reset the overload relay i0 associated with thattransmitter and open the locking circuit of the corresponding contactor relay l l by operating the manual circuit opening device 29 in its holding circuit. Where the disconnection of the transmitter is brought about manually through the operation of a switch 40, a procedure similar to the above is followed in resetting the circuit, except in that the switch 40 is restored to its initial condition instead of the relay i 1), prior to opening the locking circuit of the corresponding contactor relay H.

These two simple operations reset this portion of the control circuit to its normal condition, permitting the contacts 9 in the line to the transmitter to close and thereby provide for the application of high voltage direct current excitation to the transmitter in question.

While I have disclosed my invention in great detail, it is apparent that the embodiment described is susceptible to many modifications without departing from the scope of my invention, and I therefore, do not desire to be limited in my protection to the specific details disclosed, except as may be necessitated by the prior art and the appended claims.

I claim as my invention:

1. In combination, a low voltage alternating current supply source, a plurality of transmitters connected in multiple and utilizing high direct current voltages for operation, means for converting said alternating current supply source into direct current of relatively high voltage suitable for energization of said transmitters, switching means for connecting said direct current to each of said transmitters and means for interrupting and then restoring said supply of alternating current within an inappreciable time interval, and means for automatically disconnecting said high direct current voltage from any of said transmitters to be deenergized, Within the aforementioned period, while maintaining the high voltage connection to the other of said transmitters undisturbed.

2. In combination, a low voltage alternating current supply source, a plurality of transmitters forming a load circuit connected in multipleand utilizing high direct current voltages for operation, means for converting said alternating current supply source into direct current of relatively high voltage suitable for energization of said transmitters, switching means for applying said direct current voltage thereto, and means operable upon overload conditions in any of said transmitters for interrupting the supply of alternating current voltage deenergizing thereby.

said load circuit for an inappreciable period of time of the order of a fraction of a second and means for disconnecting said transmitter, to be deenergized, within said inappreciable period, from said direct current supply, while maintaining the connection to the other of said transmitters undisturbed.

3. In combination a plurality of transmitters, a low voltage alternating current supply source, means for transforming said low voltage alternating current source into a high voltage direct current source, means for connecting said transmitters in multiple to said high voltage direct current source, and means responsive to an abnormal condition in one of said transmitters for momentarily interrupting the alternating current supply source thereby deenergizing all said transmitters and disconnecting one of said transmitters from the high voltage direct current source during said momentary interruption, said means for disconnecting being so arranged as to be effective only for said abnormally operating transmitter and ineffective for the other of said transmitters.

4. In combination, a plurality of load circuits energized from a high voltage supply source, said source being obtained upon transformation of low voltage alternating-current supply energy, switching means operable to connect each of said load circuits to said high voltage source, means for disconnecting any of said load circuits at will from said source comprising electromagnetic actuating means including switching mechanisms for disrupting said low voltage supply prior to disconnection of one of said load circuits from said high voltage supply source, and means automatically operable for reestablishing contact of said switching mechanism upon effective disconnection of one of said load circuits While the connection of the other of said load circuits to said high voltage source remains undisturbed.

5. In combination, a plurality of load circuits energized from a high voltage supply source, said source being obtained upon transformation of low voltage alternating-current supply energy, individual switching means for said load circuits operable to connect each of said load circuits in parallel to said high voltage source, means auto matically operable upon overload conditions in any of said load circuits for disconnecting said circuits, without afiecting the connection of the other of said load circuits, comprising electromagnetic actuating means including switching mechanisms for disrupting said low voltage supply prior to disconnection of said load circuit from said high voltage supply source, and means automatically operable for reestablishing contact of said switching mechanism upon efiective disconnection of any one of said load circuits.

HENRY V. JOHNSON. 

